how to encode with lame but without a lowpass frequency and obtain in the final result the full spectrum sound. That is 22050 Hz.I have seen some mp3 files encoded by unknown encoder that was capable to do it.

A lot of work has gone into making sure LAME's default settings produce ideal results. There are knobs you can tweak, but you must realize that the MP3 format has limitations (particularly in regard to the highest frequency band) that have already been taken into account, and you're working with limited bandwidth as well. An adjustment to improve the sound in one way is quite likely to degrade the sound in another way. Do you want the higher frequencies to be preserved if it means adding noise across the entire spectrum?

Tells the encoder to use full bandwidth and to disable all filters. By default, the encoder uses some highpass filtering at low bitrates, in order to keep a good quality by giving more bits to more important frequencies. Increasing the bandwidth from the default setting might produce ringing artefacts at low bitrates. Use with care!

this was extracted from the lame 3.93.1 documentation.I think that this encoder version was the last to allow the use of the -k switch.

it warns about use with care (with low bitrates) but, what about if we use the cbr 320 bitrate ?

well, i have tried to disable the lowpass with the lame 3.98.4, and was no possible. using lowpass -1 and using lowpass 22050, etc.none of them have disabled the lowpass.

I have made tests with other lame versions, to reach teh 'famous' 3.93.1, and none of them execept this last one was able to disable.

The thing that i want to know is if the result using the '3.93.1 cbr320 -k' switch is able to produce best quality results than the 'cbr320 in 3.98.4'.I know that these frequencies are not audible, but the result is best quality... or not ?